Suggest execute validation for missing ZIP smoke

[1613358894]

Summary

• add validation-only download-smoke execute handoff fields to missing-ZIP inspect summaries when the sibling command manifest exists
• expose those fields in commands render output contracts
• document and test that the suggested handoff does not include --execute and does not download

Validation

• python -m pytest tests/test_cli_download_smoke.py -q --basetemp .pytest_tmp_missing_zip_execute_handoff -p no:cacheprovider
• python -m pytest tests/test_cli_commands.py -k download_smoke -q --basetemp .pytest_tmp_missing_zip_commands_contract -p no:cacheprovider
• python -m pytest tests/test_docs_consistency.py tests/test_docs_hygiene_script.py -q --basetemp .pytest_tmp_missing_zip_execute_handoff_docs -p no:cacheprovider
• python scripts/check_docs_hygiene.py
• python scripts/check_workspace_hygiene.py
• git diff --check
• no-download Clostridium missing-ZIP inspect rerun with sibling command manifest